Vapor generator with panel superheating means



March 28, 1961 C. J. HEROLD VAPOR GENERATOR WITH PANEL SUPERHEATINGMEANS Filed Dec. 5, 1958 2 Sheets-Sheet 1 INVENTOR Conrad J. Herold KmA. vim

ATTORNEY March 28, 1961 c. J. HEROLD 2,976,857

VAPOR GENERATOR WITH PANEL SUPERHEATING MEANS Filed Dec. 5, 1958 2Sheets-Sheet 2 Fig. 3.

INVENTOR Conrad J. Herold J} K M A4 f ATTORNEY VAPOR GENERATOR WITHPANEL SUPERHEATIN G NmANS Filed Dec. 3, 1958, Ser. No. 777,960

1 Claim. (Cl. 122-478) This invention relates to vapor generators andparticularly to modern high capacity generators which employ panel typeradiant superheaters which extend into the furnace of the vaporgenerator.

With the steadily increasing capacity that is being called for in modernutility boilers it has been necessary to employ a substantial amount ofradiant superheating surface in order to obtain the steam temperaturefor which these units are designed. It is the general practice toprovide this steam heating surface in the form of radiant panels thatextend down into the vertically disposed furnace to an area of ratherintense heat with the panels being formed of sinuously bent, internestedtubes. The panels are spaced across the furnace in rows and because ofthe length of the panels it is necessary that there be some means tolaterally support the lower ends since otherwise they would vibrate andmove around to an extent that could not be tolerated. One of the mostwidely used methods of supporting these panels is to extend a thickwalled water cooled tube, across the furnace with the tube beingprovided with spacers between which is embraced one of the tubes of eachpanel and with the tubes of each panel themselves being connectedtogether by suitable connectors which prevent relative lateral movementof adjacent tubes. This horizontal thick walled support tube, however,is itself a source of trouble in the steam generator since the furnacesof these high capacity steam generators are 40 or more feet across andthis horizontal tube is necessarily in a zone where it is subjected tovery intense heat. Stratification will occur in this tube with steamoccupying the upper portion while water occupies the lower portion andthis causes the upper portion to overheat and accordingly fail and alsocauses internal erosion in the upper portion of the tube with thiserosion occurring particularly in the lengths of the tube between thepanels where the spacer tube is exposed to extreme heat and highcombustion gas flow. While a spinning device may be positioned in thetube to eliminate the Stratification this adds a considerable pressureloss which is detrimental in natural circulation boilers and in forcedcirculation boilers would require that the pump for the circulatingsystem be of such a size as to overcome the pressure loss or drop whichwill exist in this tube and which would be greater than that in othertubes of the steam generator with it being very uneconomical to size apump for this particular support. The present invention is directed toeliminating these difiiculties.

In accordance with this invention lateral support for the superheaterpanels that extend down into the furnace of the steam generator isprovided by suitably bending a pair of adjacent tubes that line thefurnace wall next to the panel so these tubes extend from this wall intothe furnace forming a generally horizontally disposed U or loop, withthe upper run of this loop having the panel snuggly but slidablyembraced between the pair of tubes while the outer end or web and lowerrun are positioned in relatively closely spaced relation to the end ofthe atent F 2,976,857 Patented Mar. 28, 1961 panel. With thisarrangement not only is the lower end of this panel restrained frommoving laterally but this U-shaped support provides, to an appreciabledegree, a shield from the intense heat in this zone of the furnace. Thisis extremely important when it is considered that the return bends thatmake up the lower ends of the panels have the poorest heat dissipatingcapacity or heat transfer of the entire panel and are located in themost intense zone of heat of any part of the panel. They have thepoorest heat dissipating capacity because these return bends act, to anextent, as separators for foreign material with this material beingdeposited against thevtube Wall as the direction of steam flow isreversed thereby causing a thin scale of this material to form on theinside of the tube reducing the rate of heat transfer and accordinglythe cooling effect of the steam. This may result in the metal at thisturn overheating and eventually cause 'a tube failure. Accordingly,partially shielding the return beads of these panels is extremelydesirable in order that this likelihood of tube failure may be greatlyreduced if not completely eliminated.

it is an object of this invention to provide an improved vapor generatororganization employing radiant vapor heating panels extendinglongitudinally into the furnace, with the furnace being lined with heatexchange tubes.

Other and further objects of the invention will become apparent to thoseskilled in the art as the description proceeds.

With the aforementioned objects in view, the invention comprises anarrangement, construction and combination of the elements of theinventive organization in such a manner as to attain the results desiredas hereinafter more particularly set forth in the following detaileddescription of an illustrative embodiment said embodiment being shown bythe accompanying drawings wherein:

Fig. l is a somewhat diagrammatic illustration in the nature of avertical section through a high capacity vapor generator within which isembodied the present invention;

Fig. 2 is a detailed fragmentary elevational view showing the furnacewall tubes at the location where the tubes are bent laterally from thewall to provide the lateral Fig. 4 is a fragmentary perspective viewshowing two of the superheater panels embraced within the support tubeswhich are bent from the adjacent furnace wall.

Referring now to the drawings, wherein like reference numerals are usedthroughout to designate like elements, the illustrative and preferredembodiment of the invention shown therein includes an upright furnace 10which is fired with a suitable fuel generally in its lower regionthrough burners 12 with the combustion gases generated by the burningfuel passing upwardly through the furnace and out through the lateraldischarge passageway 14. The furnace is of the usual rectangulartransverse section and may be 30 ft. deep and 40 ft. wide with the innersurface of the furnace walls being lined with steam generating tubes 16which are connected at their lower ends to header 18 and communicate attheir upper end with steam and water drum 20. Water from this drumpasses down through downcomer 22 which is connected at its lower endwith pump 24 and this pump is effective to force the water through thesteam generating tubes.

The steam generated in the steam generating tubes is superheated bymeans of the superheater designated generally 24 and which includes theradiant panels 26 and the convection panels 28. Each of these panels aremade up of a group of tubes that are connected between inlet header 30and outlet header 32 with the tubes extending down from the inlet header30 through the roof of the furnace to a zone in the furnace of intenseradiant heat where they are reversely bent and extend back up to theupper end of the furnace with the downwardly extending and upwardlyextending runs of ,these tubes forming the radiant panel 26 of thesuperheater and with the returnbends being internested. These tubesextend from this radiant panel laterally adjacent the upper end of the,

furnace to the passageway 14 where they again extend downwardly and thenupwardly and through the roof to header 32 and from the convection panel28.

Radiant panels 26 are normal to and spaced across front wall 34- of thefurnace and the pair of vertically extending steam generating tubes thatline the inner surface of this front wall immediately adjacent eachradiant panel and at the location of the lower end ofthe panels are bentoutwardly to form a 'U or loop extending from the wall and which isarranged to provide lateral support for the lower end of panels 26 andto shield the return bends of these panels from some of the intenseradiant heat in the furnace. These .U bends, designated generally 36,comprise upper run 38, lower run 40 and interconnected web portion 42.As clearly shown in Fig. 4, the upper run 38 of the pair of tubes bentfrom the wall 34 adjacent panel 36 snugly embraces the paneltherebetweenwhile the web 42 and the lower run 40 are in relativelyclosely spaced relation with the return bends at the lower end of thepanel so as to partially shield the panel from the flame in the furnace.Wehportions 42 of the pair of tubes are provided with laterallyextending fins 44, as shown, with the fins that extend toward each otherabutting and being welded together throughout their" length therebyproviding a rigid construction. While the upper runs 38 of the U bendswhich embrace the panel 26 therebetween are effective to substantiallyprevent,

lateral movement or vibration of the panel they permit the panel toslide vertically so that the tubes of the panel may expand and contractas required.

At the location of the U bends 26, the tubes that line wall 34 and thatare adjacent to the tubes that are bent from this wall have a portion(40 in Figs. 2 and 3) bent slightly towards each other so as to occupy aportion of I the space normally occupied by the pair of tubes that formthe superheater support and are provided with fins 41- While I haveillustrated and described a preferred embodiment of my invention it isto be understood that such is merely illustrative and not restrictiveand that variations and modifications may be made therein withoutdeparting from the spirit and scope of the invention. I therefore do notwish to be limited to the precise details set forth but desire to availmyself of such changes as fall 3 within the'purview of my invention.

What I claim is:

A vapor generator including an upright furnace of generally rectangulartransverse section having front, rear and side walls with the furnaceexit for combustion gases being in the upper end of said rear wall,burner means including tubularpanels extending down into the furnaceofthe furnace and providing a lateral support for the I from the upperend thereof with the panels being adjacent and normal to said front walland disposed in spaced relation thereacross, each of the panels beingformed of a plurality of immediately adjacent tubes that extendvertically down into the furnace from the top thereof to a pre.determined distance where they are reversely bent in in-;

H 1 lower end of the panels comprising a pair of front wall tubesadjacent each panel having adjacent portions bent in unison from thewall and extending into the furnace to form generally a loop with thelower leg of each pair a being in adjacent relation to and below thelower end of the panel while the upper leg of the pair forms an entubeportions forming the outer end of the loops with 'the fins being inabutting relation and welded together,

the wall'tubes adjacent each of the pair of tubes bent to extend intothe furnace being finned at the location of the bent tube portion tofill the space left thereby.

References Cited in the file of this patent UNITED STATES PATENTS2,803,227 Marshall Aug. 20, 1957 r V FOREIGN PATENTS 1,065,921 FranceJan..l3, 1954

